A Century of Solar Ca <Emphasis Type="SmallCaps">ii</Emphasis> Measurements and Their Implication for Solar UV Driving of Climate

Spectroheliograms and disk-integrated flux monitoring in the strong resonance line of Ca ii (K line) provide the longest record of chromospheric magnetic plages. We compare recent reductions of the Ca ii K spectroheliograms obtained since 1907 at the Kodaikanal, Mt. Wilson, and US National Solar Observatories. Certain differences between the individual plage indices appear to be caused mainly by differences in the spectral passbands used. Our main finding is that the indices show remarkably consistent behavior on the multidecadal time scales of greatest interest to global warming studies. The reconstruction of solar ultraviolet flux variation from these indices differs significantly from the 20th-century global temperature record. This difference is consistent with other findings that, although solar UV irradiance variation may affect climate through influence on precipitation and storm tracks, its significance in global temperature remains elusive.     

Error estimates with L1 solutions

A method is given, based on the pseudoinverse of the equations of condition, to obtain error estimates for the solution in the normL ₁ of an over-determined linear system. The computational labor to obtain the errors, while not trivial, is less than that for various competing methods, particularly if there are many more equations of condition than unknowns. The error estimates for anL ₁ solution are substantially larger than those for a least squares solution of the some data. It is suggested that a complete discussion of a linear system include at least bothL ₁ and least squares solutions with their respective errors and the condition number of the linear system.     

Procedures for solving Kepler's equation

We review starting formulae and iteration processes for the solution of Kepler's equation, and give details of two complete procedures. The first has been in use for a number of years, but the second is entirely new. The new procedure operates with an iterative process that always gives fourth-order convergence and is taken to only two iterations. The error in the resulting solution then never exceeds 7×10^–15 rad.     

Photospheric line-tying conditions for the MHD stability of coronal magnetic fields

Using the localised, ballooning ordering, the effect of a density stratification on the ideal MHD stability of magnetic fields is investigated. It is found that, when the photospheric density is very much greater than the coronal value, the line tying conditons are best simulated by assuming that all coronal disturbances vanish at the photospheric boundary. This is commonly known as the rigid wall conditions.     

Fine structure of a Greenland reverse tip jet: a numerical simulation

Reverse tip jets are strong low-level winds with easterly component that form near the southern tip of Greenland. In the present study, a reverse tip jet case which occurred from 21 to 22 December 2000 was examined to clarify its fine structure using a numerical model with a horizontal resolution of 3 km. The reverse tip jet, showing the supergeostrophic wind speed with a maximum wind speed in excess of 45 m s⁻¹, extended from the east coast of Greenland to the west of Cape Farewell with anticyclonic curvature. A cloud free region coincided with the jet indicated that there was a mesoscale downdraft. Along the eastern edge of the jet, a banded cloud formed between the upstream easterly wind and the colder northerly wind that is a part of the jet and is located along the east coast. This cloud was associated with large gradients in surface wind speed, temperature, moisture, and heat flux. A maximum surface total heat flux of 300 W m⁻² coincided with the location of the jet. It is suggested that the orographic deflection by Greenland's large-scale topography as well as small-scale downslope winds behind mountains with fiords causes the reverse tip jet.     

Rapid neutron capture in supernova explosions

The implications of recent studies of the dynamics of the cores of highly evolved massive stars are considered with regard to the general problems of nucleosynthesis. The typical conditions estimated for these models are shown to be very promising for the process of element synthesis by neutron capture on a fast time scale (ther-process ofBurbidge et al., 1957).     

Collective effects in diffuse matter-antimatter plasma: II

It is shown that even very slightly ionized clouds of matter and anti-matter can interpenetrate only a little on collision. Initial interpenetration produces fast electrons and positrons from annihilation. These, in turn, produce strong magneto-hydrodynamic shocks which give the small ionized component enough energy to ionize the neutral fraction and produce a Leidenfrost layer in about ten years after which interpenetration stops.     

On the size and structure of bright solar Ca+-network cells depending on the heliographic position

From photographic recordings of some hundred bright Ca⁺-network cells on the solar disk we find evidence for a smaller size of polar cells as compared to equatorial cells by a factor of about 0.9. We do not find an indication of a dependence of the structure of the cells on the heliographic position.     

The delay between solar activity and density changes in the upper atmosphere

Since 1958 it is known that there exists a response time of the upper atmosphere to changes in solar activity. This response time is best described as the lag between the 27-day variation of solar decimeter flux and the observed density changes of the upper atmosphere. Roemer obtained as a mean observational value for this lag 1.0 ± 0.12 days. Volland's simplified version of the Harris-Priester model of the upper atmosphere is used to calculate the delay which can be expected from theory. Only the effect of solar EUV radiation is taken into account. A possible influence of the corpuscular component of the solar radiation is not included in our estimate.

The calculations are carried out for the Harris-Priester model with solar activity index and a variation of . The resulting delay is 0.6 days. The calculated amplitude of the variations of the diurnal average temperatures during the solar 27-days cycle is in very good agreement with Jacchia's empirical formula.     

The asymmetry of the velocity distribution in the rotating ring in U Gem stars

It is shown that the non-keplerian character of the rotation of the ring of gas particles in a close binary system gives too large an amplitude of the radial velocity curve if this amplitude is determined from the positions of the emission lines of the ring.